Update README.md

Author: HenriTroyot

README.md

@@ -15,7 +15,7 @@
 
 - nouislider: [site](https://refreshless.com/nouislider/), [repo](https://github.com/leongersen/noUiSlider), license: https://github.com/leongersen/noUiSlider/blob/master/LICENSE
 
-- sortablejs: [site](http://rubaxa.github.io/Sortable/), [repo](https://github.com/RubaXa/Sortable), license: MIT
+- sortablejs: [site](http://sortablejs.github.io/Sortable/), [repo](https://github.com/RubaXa/Sortable), license: MIT
 
 - ckeditor: [site](https://ckeditor.com/ckeditor-4/), [repo](https://github.com/ckeditor/ckeditor-dev), license: https://github.com/ckeditor/ckeditor-dev/blob/major/LICENSE.md